Carbohydrate-deficient Glycoprotein Research Articles

Detection of phosphoglucomutase-3 deficiency by lectin-based flow cytometry

Detection of phosphoglucomutase-3 deficiency by lectin-based flow cytometry

Comparison of Lower Extremity Joint Motion of Children with Different Inborn Errors of Metabolism

Objective: The purpose of this study is to investigate kinematic changes in children with IEMs. Introduction: The diagnosis and treatment of inborn errors of metabolism (IEMs) can be challenging as clinical presentation is highly variable. Pathological gait in children with IEM may mistakenly be considered as one in CP. Materials and Methods: Six children subsequently diagnosed with an IEM were referred for a standardized gait analysis and retrospectively recruited for a case series study. All of them were referred to have a gait analysis due to clinical impression with abnormal gait of cerebral palsy. Subjects were separated into three specific IEM conditions; Mitochondrial disease (MD), Carbohydrate-deficient glycoprotein syndrome (CDGS), or Glutaric acidemia type I (GA1). Results: Children with MD or CDGS exhibited increased knee flexion and ankle dorsiflexion at initial contact and mid-stance phase, while the children with GA1 exhibited knee hyperextension and increased ankle plantarflexion at mid-stance. Toe off timing generally occurred later in the cycle for children with IEMs. Conclusion: This indicates that the use of a gait analysis can assist clinicians’ understanding of dynamic muscle spasticity and provide a functional outcome for different treatment options. Further gait analysis of children with IEMs is necessary to validate the observed findings and substantiate the use of standardized gait analysis as part of the clinical evaluation of a child with a suspected IEM.

Significance of sugar chain recognition by galectins and its involvement in disease-associated glycosylation

Galectins are β-galactoside-binding lectins that participate in a wide range of biological processes. Galectins are distributed both inside and outside cells and are believed to have roles in both intra- and extracellular milieus. One of the well-recognized functions of galectins is stabilization of glycoproteins on the cell surface, thereby promoting stable signal transduction and transport of substances such as glucose. Glycoprotein-associated diseases, including congenital disorder of glycosylation (CDG, previously called carbohydrate-deficient glycoprotein syndrome), comprise a disease family established only in the last decade. Although numerous in vitro glycobiology studies have been performed, including investigation of glycan-galectin interactions and of galectin action in cultured cells, a few in vivo studies have investigated molecular mechanisms of galectin actions in animal models. Both in vitro and in vivo studies are needed in order to better determine the biological significance of sugar chain recognition. Hitherto, some reports have focused on the role of impaired sugar chain recognition and galectin function in the development of diverse diseases, including rheumatoid arthritis, diabetes mellitus, colitis, and cancer. We recently focused on the function of galectins in immunity and embryogenesis, and in this review we summarize the diseases related to disorders of sugar chain-galectin interaction and discuss the role of galectins as potential risk factors for some congenital and acquired diseases. These diseases are disorders of immunity, metabolism, and cell differentiation. This approach to understanding the significance of sugar chain recognition by galectins may open up a new field into the nature of glycoprotein-related diseases, including CDG.

Distinct Features of Congenital Disorder of Glycosylation Type IIx in Kuwait

Congenital disorders of glycosylation are a rare but complex group of inborn metabolic diseases that result in carbohydrate-deficient glycoproteins. Biochemical and clinical features of both types I and II of this group of disorders have been well characterized and reported from various parts of the world except the Middle East. The authors describe a patient with congenital disorders of glycosylation type IIx who presented with psychomotor retardation, development delay, hypotonia, and hepatomegaly. Computed tomography scan of the liver showed multiple hepatic focal lesions, and magnetic resonance imaging revealed mild brain and corpus callosum atrophy. This is the first report of congenital disorders of glycosylation type IIx from Kuwait that shows its prevalence and distinct features in the Middle East.

Progressive ataxia in Swedish children: a re-evaluation study.

The results of follow-up of 76 children with progressive ataxia first reported in 1988 are described with special reference to type of potential underlying metabolic diseases. In 70% of cases the clinical follow-up did not lead to reconsideration of diagnoses. Six of 23 biochemically and morphologically re-examined children got a new and definite diagnosis: 1 myoclonic encephalopathy with ragged red fibres, 2 carbohydrate-deficient glycoprotein syndrome, 1 neuroborreliosis, 1 Hallervorden-Spatz disease and 1 leucodystrophy. Different clinical groups are discussed.

A Temperature-sensitive Mutation in the Arabidopsis thaliana Phosphomannomutase Gene Disrupts Protein Glycosylation and Triggers Cell Death

Eukaryotic phosphomannomutases (PMMs) catalyze the interconversion of mannose 6-phosphate to mannose 1-phosphate and are essential to the biosynthesis of GDP-mannose. As such, plant PMMs are involved in ascorbic acid (AsA) biosynthesis and N-glycosylation. We report on the conditional phenotype of the temperature-sensitive Arabidopsis thaliana pmm-12 mutant. Mutant seedlings were phenotypically similar to wild type seedlings when grown at 16-18 degrees C but died within several days after transfer to 28 degrees C. This phenotype was observed throughout both vegetative and reproductive development. Protein extracts derived from pmm-12 plants had lower PMM protein and enzyme activity levels. In vitro biochemical analysis of recombinant proteins showed that the mutant PMM protein was compromised in its catalytic efficiency (K cat/K m). Despite significantly decreased AsA levels in pmm-12 plants, AsA deficiency could not account for the observed phenotype. Since, at restrictive temperature, total glycoprotein patterns were altered and glycosylation of protein-disulfide isomerase was perturbed, we propose that a deficiency in protein glycosylation is responsible for the observed cell death phenotype.

Congenital disorders of glycosylation: Rapidly enlarging group of (neuro)metabolic disorders

Only in the last couple of years, an ever-growing number of human genetic diseases in the synthesis of glycoproteins have been identified. Correct glycosylation of glycoproteins is essential for their biological function and the sugar chains act as biosignals for cell–cell communication, intracellular signalling, protein folding or targeting of proteins. Underglycosylation of glycoproteins, functioning as hormones, enzymes or transporters, lead to impaired bioability, decreased activity and rapid degradation. Given the overall importance of glycosylation, it is not surprising, that a disruption of the glycosylation machinery can lead to multisystemic and severe diseases. Up until now, mainly defects in the N-glycosylation pathway have been discovered and are grouped as Congenital Disorders of Glycosylation (CDG), formerly known as Carbohydrate-Deficient Glycoprotein syndromes. More recently, defects in the less well-defined O-glycosylation pathway were identified and combined glycosylation disorders in which both, the N- and O-glycosylation processes are affected.

Metabolic Disorders Associated With Neonatal Hypoglycemia

After completing this article, readers should be able to: 1. Describe four sources of glucose available to the neonate in the first 24 postnatal hours. 2. Select the best routine diagnostic test to recognize fatty acid oxidation defects. 3. List three or more metabolic disorders that can be identified by newborn screening performed using tandem mass spectrometry. Hypoglycemia is a common problem in neonates that has many causes. This review focuses on metabolic disorders that may be associated with hypoglycemia in the neonatal period. During intrauterine life, the fetus derives fuel, as glucose, from the mother via the placenta. After birth, the energy demands on the former fetus increase dramatically. The baby now must maintain its own body temperature and must undertake the work of breathing and other activities. Further, the maintenance of blood glucose levels requires glycogenolysis and gluconeogenesis. Postnatally, there are four sources of glucose: dietary glucose; glucose derived from the cleavage of more complex sugars in the gut (eg, lactose to glucose and galactose); glucose released from glycogen stores (primarily in the liver); and gluconeogenesis, in which glucose is synthesized from carbon skeletons derived from certain amino acids using energy derived from catabolism of fatty acids. Most term infants have sufficient glycogen stores to maintain blood glucose levels for several hours before gluconeogenesis is required. Infants who are breastfed in the United States typically are offered only water as a supplement to human milk during the first few postnatal days, a period when the mother’s milk supply is not yet established. In contrast, formula-fed babies receive calories by mouth by the end of the first postnatal day. Consequently, the metabolic stress of prolonged fasting occurs more frequently in breastfed than in formula-fed babies. Although breastfed babies have higher levels of ketone bodies that appear to provide adequate energy during this …

CARBOHYDRATE-DEFICIENT TRANSFERRIN (CDT)—A BIOMARKER FOR LONG-TERM ALCOHOL CONSUMPTION

Carbohydrate-deficient transferrin (CDT) is a biomarker for chronic alcohol intake of more than 60g ethanol/d. It has been reported to be superior to conventional markers like gamma-glutamyltransferase (GGT) and mean corpuscular volume (MCV). This review covers theoretical and analytical aspects, with data from controlled drinking experiments and from different population subgroups such as subjects with different liver diseases or different drinking patterns. CDT determinations are particularly indicated in (1) cases of chronic alcohol consumption and relapses after withdrawal, (2) license reapplication after driving under alcohol influence, (3) differentiating patients with enzyme-inducing medication from those with alcohol abuse, (4)congenital disorders of glycosylation such as carbohydrate-deficient glycoprotein syndrome la (CDGS la), and (5) patients treated for galactosemia. The main advantage of CDT is its high specificity, as evidenced in combination with increased alcohol consumption. CDT values are not markedly influenced by medication except in immunosuppressed patients, who may show low CDT values. In general, CDT values appear less elevated after alcohol intake in women. The main disadvantage is the relatively low sensitivity. Hence, this parameter is not suitable for screening for subjects with alcohol abuse in the general population. As CDT, GGT, and MCV are connected with chronic alcohol consumption by different pathophysiological mechanisms, a combination of these parameters will further improve the diagnostic value.

P0574 LONG TERM FOLLOW UP OF CONGENITAL DISORDERS OF GLYCOSYLATION TYPE I OR CDG I SYNDROME

Introduction: Congenital disoders of glycosylation (CDG), or carbohydrate deficient glycoprotein syndromes, form a rapidly growing group of autosomal recessive inherited disorders characterised by defects affecting the glycosylation of proteins. Fourteen CDG are identified, the most frequent is CDG Ia due to a defect in phosphomannomutase. Most CDG Ia are multisystem diseases that include severe brain involvement, early failure to thrive and feeding difficulties. Methods: We report the clinical, biological and molecular analysis of a CDG Ia patient detected by western blotting of serum glycoproteins at age 19. He was the first child of unrelated parents and was born in 1980. At age 1 month, he presented with generalised oedema, diarrhoea which started at the first feeding and anorexia. Neonatal hypotonia, nystagmus, psychomotor retardation were also present as well as inverted nipples, facial dysmorphia and lipodystrophia. Weight was 4.9kg and height 62 cm at age 7 months. Seizures started during the second year of life. At age 16, he developed a thrombosis of the left external iliac artery and the left lower limb. At age 23, he is on anormal diet, has no diarrhoea and his liver function is normal. He is unable to walk without support and receives daily heparin, phenobarbital and valproic acid. Results: Hypoproteinemia <45g/l and hypoalbuminemia were attributed to protein losing enteropathy and lymphangiectasy at 1 month of age and persisted during the first 2 years. Transaminases were elevated and severe portal fibrosis was seen on a liver biopsy at age 1. Thrombocytopenia is permanent. Coagulopathy was noted at 2 months and 10 years: PTT 25%, TCK 180, factor IX 7%. The level of antithrombin III is <5%. Cerebellar atrophy was detected on CT scan at age 2 years. Phosphomannose activity is severely decreased: 0.5 U/g prot (N>3.4). Mutation analysis of the PMM gene identified 2 mutations on the maternal allele (P20S and IVS1 + 1G->T) and a different mutation on the paternal allele (I132T). Conclusion: It is concluded that CDG Ia is a multisystem disease with severe gastrointestinal and hepatic manifestations during the first years of life. After childhood, CDG Ia has no longer digestive symptoms and becomes a non-progressive neurologic disease with peripheral neuropathy, mental retardation and seizures and a thrombotic predisposition due to decreased levels of major coagulation inhibitors, particularly as a result of impaired glycosylation of antithrombin III. A study of ten French adolescents and adult patients with CDG I is ongoing in Paris and coordinated by N Seta.

Testing for congenital disorders of glycosylation by HPLC measurement of serum transferrin glycoforms.

Congenital disorders of glycosylation (CDG), formerly named carbohydrate-deficient glycoprotein syndrome, are rare hereditary disorders caused by mutations in the genes coding for enzymes involved in the biosynthesis of glycoproteins and other glycoconjugates (1). The clinical characteristics are variable, but often include psychomotor, growth, and mental retardation from early childhood. CDG are the result of defects in the assembly and transfer (type I) or processing (type II) of the glycan moieties, and as a result, the carbohydrate chains are either completely missing (type I) or structurally abnormal (type II). CDG-Ia is the most frequent subtype, with ∼500 patients reported, whereas <100 patients have been diagnosed with types Ib–Ik and only ∼10 with type II (IIa–IId) (1)(2)(3)(4)(5). However, it is assumed that the limited awareness of CDG, together with their variable and unspecific clinical symptoms, contribute to underdiagnosis of these disorders (6)(7)(8). Another reason for underdiagnosis could be that methods for CDG testing are not generally available in clinical laboratories. Testing for CDG focuses mainly on the abnormal pattern of N-linked glycans of serum transferrin. The type I pattern is characterized by an increase of transferrin glycoforms missing one or both of the entire biantennary N-glycans (9)(10) (traditionally named disialo- and asialotransferrin, respectively, based on the number of terminal sialic acid residues), whereas type II is characterized by increased trisialo- and monosialotransferrin, indicating the presence of truncated glycans (11)(12)(13). A variety of laboratory techniques have been evaluated for this purpose, with isoelectric focusing being the most common and serving as the reference procedure to date. A sensitive HPLC method is widely used for detection of alcohol-induced changes in serum transferrin glycoforms \[i.e., carbohydrate-deficient transferrin (CDT)\] (14). This study …

Glycosylation affects the protein stability and cell surface expression of Kv1.4 but Not Kv1.1 potassium channels. A pore region determinant dictates the effect of glycosylation on trafficking.

Kv1.1 and Kv1.4 potassium channels are plasma membrane glycoproteins involved in action potential repolarization. We have shown previously that glycosylation affects the gating function of Kv1.1 and that a pore region determinant of Kv1.1 and Kv1.4 affects their cell surface trafficking negatively or positively, respectively. Here we investigated the role of N-glycosylation of Kv1.1 and Kv1.4 on their protein stability, cellular localization pattern, and trafficking to the cell surface. We found that preventing N-glycosylation of Kv1.4 decreased its protein stability, induced its high partial intracellular retention, and decreased its cell surface protein levels, whereas it had little or no effect on these parameters for Kv1.1. Exchanging a trafficking pore region determinant between Kv1.1 and Kv1.4 reversed these effects of glycosylation on these chimeric channels. Thus it appeared that the Kv1.4 pore region determinant and the sugar tree attached to the S1-S2 linker showed some type of dependence in promoting proper trafficking of the protein to the cell surface, and this dependence can be transferred to chimeric Kv1.1 proteins that contain the Kv1.4 pore. Understanding the different trafficking programs of Kv1 channels, and whether they are altered by glycosylation, will highlight the different posttranslational mechanisms available to cells to modify their cell surface ion channel levels and possibly their signaling characteristics.

Congenital disorders of glycosylation: review of their molecular bases, clinical presentations and specific therapies

Congenital disorders of glycosylation (CDG, formerly named carbohydrate-deficient glycoprotein syndromes) are a rapidly growing family of inherited disorders affecting the assembly or processing of glycans on glycoconjugates. The clinical spectrum of the different types of CDG discovered so far is variable, ranging from severe multisystemic disorders to disorders restricted to specific organs. This review deals with clinical, diagnostic, and biochemical aspects of all characterized CDGs, including a disorder affecting the N-glycosylation of erythrocytes, congenital dyserythropoietic anemia type II (CDA II/HEMPAS), and the first disorders affecting O-glycosylation. Since the clinical spectrum of symptoms in CDG is variable and may be unspecific, a generous selective screening for the presence of CDG is recommended.

Cardiac Manifestations of Carbohydrate-Deficient Glycoprotein Syndrome

A 2-month-old girl with exudative pericarditis and hypertrophic obstructive cardiomyopathy is presented. The child had characteristic dysmorphic features of carbohydrate-deficient glycoprotein syndrome, which was confirmed by serum levels of carbohydrate-deficient transferrin.

Neurological Presentation in Pediatric Patients with Congenital Disorders of Glycosylation Type Ia

Congenital disorders of glycosylation (CDG), formerly called carbohydrate-deficient glycoprotein syndromes, constitute a newly identified group of multisystem disorders characterized by defective glycosylation of N-glycosylated proteins. The objective of this work was to describe precisely neurological findings in patients with type Ia CDG (CDG-Ia) and to compare our results with the literature. We retrospectively reviewed neurological and neurodevelopmental, neuroimaging, and genetic features in ten patients with CDG-Ia who mainly presented with neurological abnormalities during childhood and therefore were referred to a neuropediatrician or a neurogeneticist. Neurological manifestations had a static clinical course, dominated by mental retardation and cerebellar dysfunction, and acute episodes: stroke-like episodes and seizures. However, microcephaly, retinopathy, and polyneuropathy were progressive. All patients had severe global neurodevelopmental delay: only one was able to walk alone at ten years of age and only one could read. Marked heterogeneity in manifestations and delay of diagnosis was noted across the patients. Cerebellar hypoplasia was found by magnetic resonance imaging in all ten patients and olivopontocerebellar hypoplasia in four patients. As in the literature, there was no clear phenotype-mutation correlation. Our findings confirm the importance of a precise and complete description of the neurological and neuroradiological phenotype delineating the phenotype of CDG-Ia to increase the likelihood of diagnosing the disease.

Síndrome de West. Análisis, factores etiológicos y opciones terapéuticas

West's syndrome (WS), which is also known as infantile myoclonic encephalopathy with hypsarrhythmia, is one of the generalized epileptic syndromes with a cryptogenic or symptomatic origin. It is an age-dependent epileptic syndrome. The latest neuroimaging techniques have enabled us to gain a better understanding of its physiopathology and to identify new aetiological factors responsible for the clinical symptoms. WS can be due to a number of aetiologies, the most notable of which are congenital errors of metabolism. The incidence of cases due to phenylketonuria or hypoglycaemia is currently diminishing, yet, there is a rise in the number of new metabolic diseases that are responsible for the symptoms of WS. These include the carbohydrate-deficient glycoprotein syndromes or biotinidase deficiency. In all cases, and especially so in those that are idiopathic, it is wise to conduct exhaustive aetiological studies, since on some occasions metabolic diseases will be shown to be responsible, and this will then modify the prognosis, therapy and genetic counselling. It is important to have a protocol for both study and therapy available for this syndrome. The therapeutic options available can be implemented after ruling out a neurometabolic disease as being responsible for the syndrome and quickly beginning treatment with vigabatrine, sodium valproate plus pyridoxine, ACTH or hydrocortisone. If there is no response then topiramate can be used. Other therapeutic options, such as the use of zonisamide, a ketogenic diet or even surgical treatment, are also analyzed.

Research agenda for pediatric gastroenterology, hepatology and nutrition: molecular basis of gastrointestinal diseases. Report of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition for the Children's Digestive Health and Nutrition Foundation.

Research agenda for pediatric gastroenterology, hepatology and nutrition: molecular basis of gastrointestinal diseases. Report of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition for the Children's Digestive Health and Nutrition Foundation.

Characterization of human transferrin glycoforms by capillary electrophoresis and electrospray ionization mass spectrometry

Carbohydrate Deficient Glycoprotein Syndrome (CDGS) is an inherited metabolic disease affecting all parts of the body. The biochemical diagnosis of this syndrome is based on the presence of a special marker in blood, Carbohydrate Deficient Transferrin (CDT), which is also a marker of chronic alcohol abuse. CDT is characterized by abnormal glycoforms of serum transferrin (Tf). In the present study, electrophoretic separation of human serum transferrin glycoforms was carried out using a bare fused-silica capillary and the glycoforms present in commercial Tf were baseline separated. The limit of detection (LOD) of human Tf was around the nmol concentration range. The LOD of the trisialo- and disialo-Tf, expressed as percentages of the tetrasialo-Tf peak area, were 0.5% for trisialo-Tf and 0.4% for disialo-Tf, and these values were appropriate for CDGS diagnosis. Moreover, Tf glycoforms were characterized using mass spectrometry (MS). The method was applied to the analysis of normal and pathological serum samples, after dilution. The results obtained suggest a way of making a rapid and simple CDGS diagnosis.

Nuevos conocimientos en la fisiopatología del cerebelo

To report recent advances regarding the physiopathology of the cerebellum in childhood.Many advances have been made in understanding the physiopathology of the cerebellum so we have limited ourselves to evaluation of the data available on the possible part played by the cerebellum in cognitive function. We then give details of the congenital disorders of metabolism in which the cerebellum is directly involved, especially neuro imaging aspects. It is impossible to give details of each and every cerebellar syndrome with neurological clinical features so we describe only four disorders: Joubert s syndrome, the Dandy Walker syndrome, carbohydrate deficient glycoprotein syndrome and finally pontocerebellar hypoplasia in its two forms of presentation. We analyze recent advances in relation to clinical and neuro imaging aspects of various cerebellar disorders.Great advances have been made in understanding the cerebellum in childhood. It is important to know about them because of their implications, especially in cognitive function.

Online Single-Step Analysis of Blood Proteins: The Transferrin Story

The serum iron transport protein human transferrin (hTf) is a glycoprotein (MW ∼79.6 kDa) containing two Asn-linked sites of glycosylation. The presence of specific glycoforms of hTf has been used as an indicator of carbohydrate-deficient glycoprotein syndrome (CDGS) or an indicator of alcohol abuse. The exact nature of the glycoforms described in the literature is controversial. In this work we demonstrate that the altered hTf glycoforms have lost one or both complete glycan side chains. Furthermore, we demonstrate using a combination of online immunoaffinity–postconcentration–mass spectrometry in conjunction with a blood spot cartridge that we can determine the relative quantities of the hTf glycoforms using <5 μL blood in under 30 min. This is in contrast to previous methods that used 1 mL and took 4 days. We show that this method can be useful to analyze hTf from CDGS and alcoholic patients.